Composite Structural Member

ABSTRACT

An inflatable mold assembly for forming a hollow composite construction member that is suitable for use as a building material has a longitudinal axis. The mold assembly further has a flexible, substantially tubular bladder wall defining an elongated inflatable cavity. A reinforcing fabric is positioned concentrically around the flexible bladder wall. A flexible air-impervious outer layer is positioned concentrically around the fabric, with the bladder wall and the outer layer defining an elongated annular space, and with the fabric being positioned within the elongated annular space.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. Ser. No. 12/891,032, issuedSep. 3, 2013 as U.S. Pat. No. 8,522,486, which is: (1) aContinuation-In-Part of U.S. Ser. No. 11/642,240, filed Dec. 19, 2006,issued as U.S. Pat. No. 7,811,495, which claimed the benefit of U.S.Provisional Application No. 60/752,233 filed Dec. 20, 2005, now expired;and (2) a Continuation-In-Part of U.S. Ser. No. 11/043,420, filed Jan.26, 2005, pending; the disclosures of all of which are incorporatedherein by reference.

BACKGROUND

Various embodiments of a composite construction member and methods ofmaking such construction members are described herein. In particular,the embodiments described herein relate to improved compositeconstruction members of the type usually suitable for use as a buildingmaterial. Examples of such members include lightweight tubular archesand beams.

In the past, there have been several types of technologies that havebeen used in order to construct short and medium span buried archbridges, as well as some underground storage facilities and tunnels.These structures are commonly arch-shaped, and typically are coveredwith a soil overburden which receives traffic or other loading.Arch-shaped construction members are also used in building constructionas structural members.

One method for providing such construction members is to use pre-castconcrete structures which are made in one location and then shipped tothe construction site. Another system includes the use of cast-in-placeconcrete structures which are formed at the construction site and thenlifted into place by cranes or the like. Yet another technology includesthe use of metallic pipe structures. Further, metallic and steelreinforced concrete can be used as construction members. Increasingly,composite materials are being used in the construction industry.

Important factors in selecting construction materials include cost ofthe materials, ease of transport and installation, durability, weight,length of time for construction, need for lifting equipment forinstallation, complexity of the construction sequence, overallperformance, and overall installed cost. It would be advantageous ifimproved construction materials and systems for the constructionindustry could be developed.

SUMMARY

The present application describes various embodiments of a compositeconstruction member. In one embodiment, an inflatable mold assembly forforming a hollow composite construction member that is suitable for useas a building material has a longitudinal axis. The mold assemblyfurther has a flexible, substantially tubular bladder wall defining anelongated inflatable cavity. A reinforcing fabric is positionedconcentrically around the flexible bladder wall. A flexibleair-impervious outer layer is positioned concentrically around thefabric, with the bladder wall and the outer layer defining an elongatedannular space, and with the fabric being positioned within the elongatedannular space.

In another embodiment, a system for making a rigid hollow compositeconstruction member includes an inflatable mold assembly for a hollowcomposite construction member suitable for use as a building material.The inflatable mold assembly is elongated and has a longitudinal axis.The mold assembly further has a flexible, substantially tubular bladderwall defining an elongated inflatable cavity. A reinforcing fabric ispositioned concentrically around the flexible bladder wall. A flexible,air-impervious outer layer is positioned concentrically around thefabric, with the bladder wall and the outer layer defining an elongatedannular space. The fabric is positioned within the space. Apparatus forapplying tension to the fabric in a longitudinal direction, apparatusfor introducing a fluid into the cavity to inflate the tubular bladderwall are provided, and apparatus for infusing the elongated annularspace and the fabric with a rigidification material to form a rigidhollow composite construction member are provided.

In another embodiment, an inflatable mold assembly for forming a hollowcomposite construction member suitable for use as a building materialhas a longitudinal axis. The mold assembly further has a flexible,substantially tubular bladder wall defining an elongated inflatablecavity. A reinforcing fabric is positioned concentrically around theflexible bladder wall. A flexible air-impervious outer layer ispositioned concentrically around the fabric, with the bladder wall andthe outer layer defining an elongated annular space. The fabric ispositioned within the space. An intermediate member is positionedconcentrically within the elongated annular space between thereinforcing fabric and the tubular bladder.

In another embodiment, a hollow composite construction member suitablefor use as a building material includes a tubular primary reinforcementmember that has a hollow interior and is formed from a first material. Ashear transfer member is bonded to an inside surface of the tubularprimary reinforcement member. A secondary reinforcement material atleast partially fills the hollow interior of the tubular primaryreinforcement member. The secondary reinforcement material is differentfrom the first material.

In a further embodiment, a hollow composite construction member suitablefor use as a building material includes a tubular primary reinforcementmember that has a hollow interior and is formed from a first material.One of an array of grooves and ridges is formed on an inside surface ofthe tubular primary reinforcement member. The array defines a sheartransfer member. A secondary reinforcement material at least partiallyfills the hollow interior of the tubular primary reinforcement member.The secondary reinforcement material is different from the firstmaterial.

Other advantages of the composite construction member will becomeapparent to those skilled in the art from the following detaileddescription, when read in light of the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of portions of an inflatable tubularmold assembly for making composite construction members, the moldassembly being in a deflated condition.

FIG. 2 is a schematic cross-sectional view in elevation of a portion ofthe mold assembly in a partially inflated condition.

FIG. 3 is a schematic view similar to that of FIG. 2, with the moldassembly fully inflated, and with a partial vacuum applied to the moldassembly.

FIG. 4 is a schematic view similar to that of FIG. 2, with the moldassembly undergoing rigidification.

FIG. 5 is a schematic illustration showing an inflated mold assemblybeing bent around a formwork while an external force is being appliedtangent to a curvature of the inflated curved mold assembly at a pointof contact with the formwork, and showing a device for applying tensionto an end of the curved mold assembly.

FIG. 6 is a schematic illustration of a rigidified inflatable compositestructure after being removed from a formwork.

FIG. 7 is an enlarged schematic illustration of an area in FIG. 6showing a braid angle of fibers in rigidified inflatable compositestructure relative to the hoop direction of the rigidified inflatablecomposite structure.

FIG. 8 is a schematic illustration taken along the line 8-8 in FIG. 6,showing a rigidified inflatable composite structure filled with a loadbearing material.

FIGS. 9 through 11 are schematic illustrations of variouscross-sectional shapes of additional rigidified inflatable compositestructures filled with a load bearing material.

FIG. 12 is a schematic perspective view of a bridge arch formed withhybrid composite construction members according to the invention.

FIG. 13 is an elevational view of a first embodiment of the hybridcomposite construction member illustrated in FIG. 12.

FIG. 14A is a first transverse cross-sectional view taken along the line14-14 in FIG. 13, showing the hollow composite construction tube withthe concrete removed.

FIG. 14B is a second transverse cross-sectional view taken along theline 14-14, showing concrete within the hollow composite constructiontube.

FIG. 15 is a perspective view of a portion of a first embodiment of theshear transfer layer illustrated in FIGS. 14A and 14B, with the rest ofthe hybrid composite construction member removed.

FIG. 16 is a perspective cross-sectional view of a second embodiment ofa hybrid composite construction member.

FIG. 17 is a perspective cross-sectional view of a third embodiment of ahybrid composite construction member.

FIG. 18 is a schematic cross-sectional view in elevation of a portion ofa first alternate embodiment of the mold assembly illustrated in FIG. 2.

FIG. 19 is a schematic cross-sectional view in elevation of a portion ofa second alternate embodiment of the mold assembly illustrated in FIG.2.

FIG. 20 is a schematic cross-sectional view in elevation of a portion ofa third alternate embodiment of the mold assembly illustrated in FIG. 2.

FIG. 21 is a schematic cross-sectional view in elevation of the fabriclayer illustrated in FIG. 20, showing the fabric layer infused withrigidification material and the mold pattern member removed.

FIG. 22 is a schematic cross-sectional view in elevation of the fabriclayer illustrated in FIG. 20, showing the fabric layer infused withrigidification material and the mold pattern member bonded to the fabriclayer.

FIG. 23 is a schematic cross-sectional view in elevation of a portion ofthe mold assembly illustrated in FIG. 4, showing an alternate embodimentof the vacuum opening.

FIG. 24 is a schematic cross-sectional view in elevation of a portion ofthe mold assembly illustrated in FIG. 4, showing a first alternatelocation of the rigidification material inlet.

FIG. 25 is a schematic cross-sectional view in elevation of a portion ofthe mold assembly illustrated in FIG. 4, showing a second alternatelocation of the rigidification material inlet.

DETAILED DESCRIPTION OF THE INVENTION

Current technologies for producing curved composite structures from aninflatable tubular mold assembly are limited by fabric architecture. Inconventional methods for making composite structures from inflatablemold assemblies, each unique curve geometry requires a unique fabricarchitecture, which makes it very costly to design and produce a widerange of curved member geometries for the inflatable mold assemblies.With the embodiments illustrated, it is possible to produce a wide rangeof curved tubular fiber-reinforced polymer composite structural membersby rigidifying the inflatable composite structure made with a singleinflatable mold assembly, with various curvatures being achievable eventhough the starting inflatable mold assembly has a single parent fabricarchitecture. This parent fabric architecture may vary, and still becapable of producing members having any continuous curvature.

The embodiments illustrated and described herein include curved tubularfiber-reinforced polymer or plastic (FRP) composite structural membersthat are made with an inflatable mold assembly and formed around acurved support and infused with a rigidification material, such as anorganic or inorganic polymer material. Continuous fibers that arelongitudinally oriented are substantially prevented from buckling whenformed to a large curvature, even on the interior side of the structure,by tensioning the ends of the fabric as the rigidification material isinfused. This greatly improves the load carrying capacity of the curvedtubular fiber-reinforced polymer composite structural member.

The curved tubular fiber-reinforced polymer composite structural memberscan be produced without structurally significant or substantiallyvisible fiber wrinkling by using a tensioned braided fabric over aninflatable mold. Because the fibers may be placed close to thelongitudinal axis of the inflatable mold without substantial fiberwrinkling or buckling, the ultimately produced curved tubularfiber-reinforced polymer composite structural member is capable ofefficiently supporting multiple types of loadings for many structures,including but not limited to curved arched bridges, airplane hangars,buried tunnels and bunkers, rapidly-deployable buried arch bridges andlong-span culverts.

In one embodiment, a method for forming a curved tubularfiber-reinforced polymer composite structural member of the typesuitable for use as a building material is disclosed. The method forforming such curved tubular fiber-reinforced polymer compositestructural members eliminates or substantially reduces any of the fiberbuckling or wrinkling which causes weaknesses in a finishedreinforcement structure. In certain embodiments, the fabric layercomprises a three-dimensional braided fibrous fabric material which isinfused with a suitable rigidification material, such as a resin.

Referring now to FIGS. 1 through 4, an inflatable tubular mold assembly202 defines an interior cavity 201. FIG. 1 shows the inflatable moldassembly 202 in a deflated condition. While the inflatable mold assembly202 schematically shown in the figures has a generally circularcross-sectional shape when fully inflated, it is to be understood thatthe specific dimensions of the inflatable mold assembly 202 are guidedby the end use application for which the inflatable mold assembly 202 isbeing used. For example, the exterior shape of the inflatable bladder204 in the inflatable mold assembly 202 can have a generally circular,oval, or other useful structural configuration (as shown, for example,in FIGS. 9 through 10). In another embodiment, the inflatable bladder204 can have a cross-section that has a shape that approximates thecross-sectional shape of an I-beam, as shown in FIG. 11.

The inner cross-sectional dimension 203 as shown in the FIGS. 2 through4 is the diameter of the interior of the inflatable bladder 204 when thebladder is inflated. The outer cross-sectional dimension 205 is thediameter of the exterior of the inflatable bladder 204 and the diameterof the interior of the rigidified composite structure 238, as best shownin FIG. 6. Regardless of the geometric shape of the cross-section of theinflatable mold assembly 202, the curved tubular fiber-reinforcedpolymer composite structural member 238 (shown in FIG. 6) resulting fromuse of the inflatable mold assembly 202 is a composite member that isconsidered to be tubular as described herein.

Also, in certain other embodiments illustrated and described herein, thecross-sectional dimension 205 of the inflatable bladder 204 can varyalong its axial or longitudinal length. In such embodiments, thediameter, or major outer cross-sectional dimension 205 of the inflatablebladder 204 can vary such that the finished curved tubularfiber-reinforced polymer composite structural member 238 can havedifferent cross-sectional dimensions at different locations, dependingon the needs of the end use application. For example, in certain end useapplications, such as for example, an arch, it may be desired that lowerportions of the inflatable mold assembly 202 adjacent the ground have alarger cross-section in order to add additional support for the upperportions of the finished curved tubular fiber-reinforced polymercomposite structural member 238.

The inflatable mold assembly 202 includes at least one tubularinflatable bladder 204, at least one reinforcing fabric, such as areinforcing flexible fabric layer 206, and at least one air-imperviousouter layer 208. The interior wall 207 of the inflatable bladder 204defines the elongated inflatable cavity, 201. The reinforcing flexiblefabric layer 206 is positioned concentrically around the inflatablebladder 204. The flexible air-impervious outer layer 208 is positionedconcentrically around the flexible fabric layer 206, with the inflatablebladder 204 and the air-impervious outer layer 208 defining an elongatedinterstitial space 226 (i.e., the space between the flexible fabriclayer 206 and the inflatable bladder 204), with the flexible fabriclayer 206 being positioned within the space 226. When thecross-sectional shape of the inflatable bladder 204 is approximatelycircular, the elongated space has a substantially annular cross-section.

In certain alternative embodiments, the tubular inflatable bladder 204is made of a suitably flexible air impervious material. Examples ofmaterials that can be used for the tubular inflatable bladder 204 arenylon, Mylar, urethane, butyl rubber, high density polyethylene, vinyl,polyester, reinforced rubber, and silicone. Other materials can also beused. In certain embodiments, the flexible fabric layer 206 comprises afibrous material having a desired pattern or geometry of fibers, such asbraided or woven fibers. In certain alternative embodiments, the fabriclayer can comprise one or more types of fibers such as, for example,glass, carbon, polyethylene, polyester, aramid fiber, and mixturesthereof. The air-impervious outer layer 208 can be any suitable flexibleair impervious material, such as, for example, nylon, Mylar, urethane,butyl rubber, high density polyethylene, vinyl, polyester, reinforcedrubber, and silicone.

In the embodiment shown, the inflatable mold assembly 202 is elongated,having a longitudinal axis 210. The inflatable mold assembly 202includes a first cap member 212 at a first end 214 of the inflatablemold assembly 202, and a second cap member 216 at an opposed, second end218 of the inflatable mold assembly 202. The cap member 212 includes asealable opening 219 through which a fluid material can flow to inflatethe inflatable mold assembly 202. In certain embodiments, for example,the fluid material can be gaseous (such as air), or liquid (such aswater). Although the mold is shown as being elongated, it is to beunderstood that it need not be elongated.

FIG. 2 shows the inflatable mold assembly 202 in a partially inflatedcondition where air is being directed into the interior cavity 201 ofthe tubular inflatable bladder 204 through the opening 219. As shown inFIG. 3, the air-impervious outer layer 208 can include a sealable vacuumopening 220 through which air can be removed from the space 226 betweenthe air-impervious outer layer 208 and the tubular inflatable bladder204. It is to be understood that the space 226 is at least partiallyfilled with the flexible fabric layer 206. A suitable device forremoving air in the space 226 is a vacuum pump P, run by a motor M,although other devices can be used. The vacuum opening 220 can be placedanywhere along the length of the inflatable mold assembly 202, includinga position at one end of the inflatable mold assembly 202. Any number ofopenings 220 can be used. It should be understood that the use of anevacuation mechanism is optional, such as, for example, when a resintransfer molding process is used.

During the infusion of the fluid rigidification material 232, such as aresin, the rigidification material is driven or pumped under a pressuredifferential via rigidification material inlet or resin port 234,through the space 226. At the same time, typically, gas may be removedfrom the space 226. Any number of resin ports 234 can be used. The resinports 234 can be placed in the end of the inflatable mold assembly 202as shown, or through the air-impervious outer layer 208 anywhere alongthe length of the inflatable mold assembly 202. The resin is infusedinto and permeates the flexible fabric layer 206. The apparatusdisclosed for infusing the rigidification material 232 into the space226 is merely illustrative, and any suitable system for infusing theflexible fabric layer 206 with the rigidification material can be used.

FIG. 4 shows the rigidification material 232 fully permeating theflexible fabric layer 206. The rigidification material can be anyorganic or inorganic material that can be pumped into or infused intothe space 226, and which then sets or hardens into a rigid or semi-rigidmaterial. Examples of organic materials include thermo-set resins, suchas vinyl esters, polyesters, epoxies and the like. Other inorganicmaterials, such as cements or grouts can be used for the rigidificationmaterial. Once the rigidification material 232 is positioned within thespace 226 and the rigidification or setting of the material takes place,a composite construction member, such as the curved tubularfiber-reinforced polymer composite structural member 238 shown in FIG.7, is formed. The curved tubular fiber-reinforced polymer compositestructural member 238 is primarily useful as a building material,although it can be used for other purposes.

As shown in FIG. 5, during the molding process the inflatable moldassembly 202 is positioned against, or at least partially in, a formwork240, with the inflatable mold assembly 202 bent around or otherwise madeto conform to the formwork 240. In the embodiment shown, the formwork240 has a continuous semi-circular shape. The formwork 240 facilitatesbending the inflatable mold assembly 202 to the desired shape duringforming. The formwork 240 can have any shape suitable for producing acomposite construction member of the required configuration.

It will be understood that the formwork 240 can have any continuousgenerally curved shape, including compound curves and non-planar curves.In some embodiments, the formwork 240 can have non-round side walls suchthat the inflatable mold assembly 202 can be formed into a compositestructure having cross-sectional shapes that are not circular. FIG. 9shows a rounded hexagonal outline for a composite structure 268. FIG. 10shows a rounded square outline for a composite structure 270. FIG. 11shows an approximately I-beam shaped outline for a composite structure272.

Optionally, the rigidified composite structure 238 can be filled with aload bearing material 244, such as, for example, material selected fromthe group including non-shrink concrete, expansive concrete, non-shrinkgrout, expansive grout, foam, sand, and the like, as shown in FIG. 8.

It is to be understood that a suitable external force can being appliedtangent to a curvature of the inflatable mold assembly 202 at a point ofcontact when the inflatable mold assembly 202 is being formed into agenerally arcuate longitudinal shape. Also, while the formwork 240 shownin the Figures herein supports the inflatable mold assembly 202 along aninterior arc 202 a of the inflatable mold assembly 202, as shown in FIG.6, it may be also possible for the formwork 240 to provide the desiredcurvature for the inflatable mold assembly 202 on an exterior arc 202 bof the inflatable mold assembly 202.

Advantageously, many different shapes and configurations of therigidified composite structure 238 can be formed using only one,generally universal type, or architecture, of flexible fabric layer 206.The maker of the inflatable mold assembly 202 is therefore able to use asingle type or design of fabric architecture to produce a wide varietyof curved tubular fiber-reinforced polymer composite structural membershaving any desired curvature.

In certain embodiments of the methods described herein, a suitableamount of tension is applied to the fabric in one or both of the hoop(radial) and/or longitudinal (axial) directions to minimize, andoptimally substantially eliminate, fiber wrinkling and buckling in thefabric, even when the inflatable mold assembly 202 is bent. The suitableamount of tension may vary, but as used herein, a suitable amount oftension may be an amount of tension which causes a stress in the fibersof about less than about 2 percent of the fiber's ultimate tensilecapacity. In the embodiments illustrated and described herein, a tensionforce which causes within the range of from about 30 p.s.i. to about1000 p.s.i. of stress in the fibers is applied. Once the compositestructure 238 becomes rigid, the outer layer 208 and the bladder 204 ofthe mold assembly 202 may be removed.

FIG. 7 is an enlarged schematic illustration of an area in FIG. 6showing a braid angle θ of some of the fibers 250 in the flexible fabriclayer 206 relative to the hoop direction 252 of the inflatable moldassembly 202. The hoop direction 252 is that direction which, iffollowed, would be the shortest planar closed path along the surface ofthe cross section. For clarity in FIG. 7, most of the fibers in thefabric have been left out, so that the path of the remainingrepresentative fibers is more readily seen. The included angle, θ, isthe off hoop direction angle of the fiber. The fibers follow acontinuous approximately helical path along the surface of the flexiblefabric layer 206 from one end to the other. In FIG. 7 only one fiberangle is shown but multiple layers and angles for each layer may be usedin any combination selected for this process, and the angle ofindividual fibers may vary around the cross-section or along thelongitudinal length of the rigidified composite structure 238.

If any specific fiber is not parallel to the hoop direction 252, thenthe fiber is oriented in a non-hoop direction, and its deviation fromthe hoop direction can be measured by the angle θ. Fibers that areoriented at an angle θ that is above a threshold level, such as, forexample, 30 degrees, can be considered to have a significantlongitudinal component, i.e., they have a significant component in thedirection of the longitudinal axis 210. These fibers can be consideredto be generally longitudinally extending fibers. The longitudinallyextending fibers in the flexible fabric layer 206 are prevented frombuckling on a large curvature while the inflatable mold assembly 202 isbeing bent during the molding process by tensioning the flexible fabriclayer 206 as the resin is infused into the flexible fabric layer 206.These are critical fibers from a structural viewpoint, as they carry thebending stresses in the member. Unlike the off-hoop fibers, thehoop-oriented fibers are not susceptible to buckling when a largecurvature is applied to the mold assembly.

The curved tubular fiber-reinforced polymer composite structural member238 can be produced without substantial fiber wrinkling of the generallylongitudinally extending fibers, i.e., the fibers initially oriented atan angle greater than about 30 degrees. This is because when asubstantial portion of the generally longitudinally oriented fibers aretensioned during the infusion and curing of the resin, the off-hoopfibers are brought into and held in their designed alignment along theouter surface of the inflatable bladder 204, effectively minimizing oreliminating fiber wrinkling or buckling. In certain embodiments, theflexible fabric layer 206 is made with a simple set of repeatingpatterns such as woven or braided fabrics that have bundles or stands ofsimilarly oriented fibers set in a repeating pattern or desired fabricarchitecture.

The exemplary methods illustrated and described herein allow for theformation of structural composites that can have any desired shape. Theexemplary methods further eliminate the need to first form a fabric thathas sections of the fabric material with different weave patterns orfiber configurations in order to form shaped structures.

In certain embodiments, it is desired that certain of the fibers, orbundles of fibers, be oriented, either by tensioning or by theiroriginal orientation, into an off-hoop direction of between about 30 and90 degrees. The restrained or tensioned off-hoop oriented fibers retaintheir desired orientation without buckling or wrinkling even when theinflatable mold is bent, thereby adding strength to the ultimate curvedtubular fiber-reinforced polymer composite structural member 238. Duringthe tensioning of the fabric, the fibers, or bundles of fibers areeither pulled or allowed to relax into the desired off-hoop orientation.

It can be seen that by using a flexible fabric layer 206 that isconstructed properly, and by using tensioning during the bending andresin infusing process, a single fabric design or architecture can bemade to accommodate many different bending configurations. Consequently,the flexible fabric layer 206 is structured to be capable of conformingto molds shaped into various curvatures while still being held undertension.

In certain embodiments, the amount of tension applied to the fabricnecessary to overcome fiber wrinkling can be a small fraction of theultimate tensile capacity of the fabric. The tension on the fabric canbe applied using any suitable device, such as a gripping device. Oneexample of such a gripping device is shown schematically in FIGS. 3through 5 where gripping systems 246 and 248 are positioned at the ends214 and 218 of the inflatable mold assembly 202, respectively. Thegripping systems apply tension to the flexible fabric layer 206. Thegripping systems 246 and 248 can be any mechanisms suitable forconnecting to and applying tension to the flexible fabric layer 206. Thegripping systems 246 and 248 can be in the form of end rings, or can bea pneumatic expandable plug or a mechanical plug. Further, the elongatedinflatable mold assembly 202 can include the vacuum opening 220positioned outside of the gripping systems, a vacuum opening positionedbetween the gripping systems, or a vacuum opening positioned inside thegripping systems, as shown in FIG. 23 at 220′. Also, the elongatedinflatable mold assembly 202 can include a rigidification material inletpositioned outside of the gripping systems, as shown in FIG. 24 at 234′,between the gripping systems, as shown in FIG. 25 at 234″, or inside thegripping systems, as shown in FIG. 4 at 234. The tension applied by agripping system can also serve to keep the inflatable mold assembly 202in contact with the formwork 240. In some designs of the inflatable moldassembly 202, the mere inflation of the inflatable bladder 204 issufficient to cause the fibers to be placed under tension. In such acase, the gripping systems 246 and 248 may act to restrain or controlthe application of tension to the fibers.

In the embodiments where tension is applied to the flexible fabric layer206, the tensioning reduces fiber waviness and increases the weavepattern uniformity, thereby ultimately producing completed curvedtubular fiber-reinforced polymer composite structural members 238 havinga much higher load carrying capacity than would be produced usingotherwise identical un-tensioned fibers. Tensioning of the flexiblefabric layer 206 also produces a marked reduction in variation offinished product properties. Also, when the tension is applied to theflexible fabric layer 206, any fibers that reorient will be reorientedby the tensioning closer to the longitudinal axis of the member, therebyultimately increasing the strength of the final curved tubularfiber-reinforced polymer composite structural member 238. In someembodiments, the fibers of the flexible fabric layer 206 are allowed torealign without substantial wrinkling or buckling as the inflatable moldassembly 202 is being curved. In some embodiments, during the tensioningof the fabric, the gripping of the ends 214 and 218 allow certain of thefibers which are under much higher tension than adjacent fibers to slipuntil the load is redistributed.

In certain embodiments, the desired tension can be achieved orestablished before final inflation pressure of the tubular inflatablebladder 204 is reached. For example, the gripping systems 246 and 248can be tightened on the flexible fabric layer 206 prior to finalinflation of the tubular inflatable bladder 204. In other embodiments,once the predetermined geometric shape is achieved, tensioning due tomold elongation motivated by increased bladder pressure will begin tooccur.

In certain embodiments, rigidification of the inflatable mold assembly202 can proceed by infusing the fabric with a resin while the fibers areunder tension. Also, the forming of the curved tubular fiber-reinforcedpolymer composite structural member 238 can be carried out in severaldifferent arrangements of steps, including, for example:

i) positioning a fabric layer over an inflatable tubular wall, inflatingthe tubular wall to shape the fabric, and infusing the fabric with arigidification material;

ii) positioning a fabric layer over an inflatable tubular wall,inflating the tubular wall to shape the fabric, bending the inflatedtubular wall into a desired shape, and infusing the shaped fabric with arigidification material;

iii) inflating a tubular wall, positioning a fabric layer over theinflated tubular wall, bending the inflated tubular wall and fabric intoa desired shape, and infusing the shaped fabric with a rigidificationmaterial; and

iv) positioning a fabric layer over an inflatable tubular wall,partially inflating the tubular wall to shape the fabric, bending theinflated tubular wall into a desired shape, completing the inflation ofthe tubular wall, and infusing the shaped fabric with a rigidificationmaterial. In all of the above arrangements, the fabric is subjected totension forces.

In an alternate embodiment, the flexible fabric layer 206 ispreimpregnated with a resin, and the rigidification process is initiatedafter or during the shaping process by any suitable mechanism to createthe curved tubular fiber-reinforced polymer composite structural member.The rigidification of the resin can be initiated by the infusion of achemical initiator or catalyst, by the application of heat or light, orby any other suitable method.

In another embodiment, a plurality of the elongated inflatable moldassemblies are arranged together, with tension applied to the fabric ofeach mold assembly. Each of the plurality of mold assemblies is shapedto a desired shape while maintaining the fabric under tension. Thereinforcing fabric in each mold assembly is infused with arigidification material, and the rigidification material can be infusedin each of the mold assemblies either separately or at the same time. Inthis manner, after the rigidification material is hardened whilemaintaining the fabric in tension, a multitude of curved tubularfiber-reinforced polymer composite structural members can be formed. Themultitude of elongated inflatable mold assemblies can be formed to thesame curvature, or can be configured with different curvatures.

The illustrated inflatable mold assembly 202 can be viewed as aprecursor for a curved tubular fiber-reinforced polymer compositestructural member suitable for use as a building material. The elongatedinflatable mold assembly 202 can be used to make curved tubularfiber-reinforced polymer composite structural members in any desiredsuitable location, such as a construction site of a building, buriedbridge structure, or other structure where curved tubularfiber-reinforced polymer composite structural members are needed.Further, the curved tubular fiber-reinforced polymer compositestructural members can be filled in place with any desired material,such as non-shrink concrete, expansive concrete, non-shrink grout,expansive grout, foam, and sand. Also, a construction kit, including oneor more of the elongated inflatable mold assemblies can be prepared andshipped to a construction site. Such a kit could optionally include asupply of compressed air to inflate the tubular bladder, a source ofresin ingredients, a source of vacuum, and a framework suitable both toshape the inflatable mold assemblies during rigidification of theproduct, and to supply tension during the infusion of the rigidificationmaterial. Such a kit can be a self-contained pre-assembled kit forproducing curved tubular fiber-reinforced polymer composite structuralmembers of any desired curvature.

The embodiments illustrated in FIGS. 12 through 22 relate to theconstruction of hollow composite construction members having a hollowinner cavity at least partially filled with a secondary structuralreinforcing material to form a hybrid composite construction member. Asused herein, the term “hybrid composite” is defined as a compositeincluding at least one known composite, such as but not limited tocarbon fiber with polymer resin matrix, which is formed as a compositewith one or more other materials, such as but not limited to concrete,polymer concrete, Portland cement, and short fiber reinforced polymerconcrete.

In many applications, such as but not limited to bridge arches, beams,tunnel supports, and building frame components, it is desirable toincrease the load capacity and/or stiffness of a primary reinforcementmember. Referring to FIG. 12, a portion of a bridge arch is shown at300. The bridge arch 300 includes a plurality of hybrid compositeconstruction members 302, also shown in FIG. 13. The ends 302E of thehybrid composite construction members 302 are embedded in a concretefooting 304. In the illustrated embodiment, the hybrid compositeconstruction members 302 are covered with decking material, such ascomposite decking 306.

A hybrid composite construction member 302 includes a primaryreinforcement member or hollow composite construction tube 308. Thehollow composite construction tube 308 may be any desired and suitablyrigid tube, such as the FRP tube 238 described herein above.

The load capacity and/or stiffness of the primary reinforcement memberor hollow composite construction tube 308 may be increased by at leastpartially filling the hollow interior of the tube 308 with a secondarystructural reinforcement material 310 such as but not limited toexpansive or non shrink concrete, expansive or non shrink grout, polymerconcrete, and structural foam.

The load capacity of the hollow composite construction tube 308 may beincreased to more than the sum of the separate capacities of the primaryand secondary members 308 and 310 in a number of ways. In one example,it is desirable to make the cross-section of the composite constructiontube 308 larger to increase the moment of inertia, which increases thenet structural cost efficiency of the composite construction tube 308under high loads. Normally, there is an upper limit to the benefit ofincreasing this cross-sectional dimension without increasing the wallthickness of a tubular structure, such as the composite constructiontube 308. This upper limit exists in tubes where the failure modechanges from material failure to local buckling failure, and is oftenthe result of too high of a diameter to wall thickness ratio.Advantageously, the secondary reinforcement material 310 may be added torestrain local buckling of the wall of the primary reinforcement. Insuch an embodiment, the maximum diameter to wall thickness ratio issignificantly increased, thereby allowing an increase in structuralefficiency in the primary reinforcement.

The combination of the primary reinforcement composite constructionmember or tube 308 and secondary reinforcement material 310 becomes ahybrid composite construction member when there is composite actionbetween the composite construction tube 308 and secondary reinforcementmaterial 310. As is known to one skilled in the art, composite actionoccurs when there is substantial resistance to slippage between the twomaterials at their interface, such as the interface 322 between the tube308 and the secondary structural reinforcement material 310 describedbelow. Hybrid composite construction members 302 are desirable because aproperly arranged hybrid composite construction member 302 comprisingtwo or more materials has the potential to offer better mechanicalproperties than the sum of the mechanical properties of the componentparts of the hybrid composite. As composite action is increased,mechanical properties can be further improved, up to the point wherecomplete strain compatibility between the two materials at the interfaceis achieved. For example, in one non-limiting example, a hybridcomposite construction member 302 includes a primary reinforcement orhollow composite construction tube 308 formed from FRP. Such a hollowcomposite construction tube 308 formed from FRP typically has lowercompression strength relative to tension strength. Therefore, in purebending, combined bending and axial compression loading, and a varietyof other loading conditions, its initial failure load is determined byits compression strength. Many commonly selected secondaryreinforcements, such as concrete, have lower tension strength thancompression strength, so in pure bending, and also a variety of otherloading conditions, the failure load of unreinforced concrete isdetermined by its tension strength. Thus, using the representative butnot exclusive example of pure bending, the sum of the pure bendingcapacities of each of the FRP tubes 308 and the concrete alone are bothmuch lower than the bending capacity and stiffness of the two togetherin a hybrid composite structure. In such a hybrid composite structure,the secondary reinforcement material 310 (concrete in this example) mayaugment the compression strength of the FRP tube 308, while the FRP tube308 also augments the tensile strength of the concrete.

Minimum stiffness is often the governing property for structural designin applications and structural systems such as bridges where there aremaximum deflection limits. Again using the representative but notexclusive example of pure bending, the bending stiffness of the hybridcomposite construction member 302 is much higher than the sum of thepure bending stiffness of each of the FRP tube 308 and the concrete 310alone, because of the composite action between the primary and secondaryreinforcements 308 and 310, as described above.

There are many other benefits to the hybrid composite constructionmembers 302 described herein over the structurally separate combinationof the two members. In order for the primary and secondary reinforcementto work in concert as a single structure however, there must besubstantial shear transfer between the two components. Examples of suchshear transfer may be observed in the present state of the art in steelrebar reinforced concrete, bonded skins in foam core boat decks, andother applications known in the present state of the art.

In the past, methods to achieve shear transfer in tubular structuresfilled with concrete have been limited to creating a chemical bond usinga layer of adhesive. This approach, while effective, limits thestructure to embodiments of the type where a solid section ispre-fabricated, and then a tube-like structure is bonded to the outsidesurface in a post-process.

In the case where the secondary reinforcement material is cast inside ofan FRP structural tube, prior approaches to achieving shear transferhave included: assuming, for load calculations, that no shear transferoccurs, using weak secondary bonding directly between the two materialsto gain some degree of shear transfer, and using studs or rebar placedthrough the wall of the tubular structure. For example, in somesecondary reinforcement materials, such as concrete, polymer concrete,and cured in place foam, at least some shear transfer is achievedthrough some degree of chemical bonding during the curing process forthe secondary reinforcement material, which can be somewhat beneficialto structural efficiency. Testing has shown however, that chemicalbonding can be insufficient to provide enduring composite action withwhich to develop the maximum bending strength, stiffness, and fatiguepotential of the hybrid composite construction member 302, describedherein.

Unfortunately, each of these shear transfer approaches often results insignificant fabrication disadvantages and/or provides less than idealshear transfer. The benefits of shear transfer have been largelyunavailable in concert with the unique benefits achievable in systemswhere the secondary reinforcement material is cast in place inside anexisting tubular FRP structure. Known reinforced FRP tubes havetherefore not taken full advantage of the composite action phenomenon.

Referring now to FIG. 13 through 15, a first embodiment of a hybridcomposite construction member is shown at 302. FIG. 14A is a firstcross-sectional view of the hollow composite construction tube 308,shown with the secondary reinforcement 310 removed for clarity. FIG. 14Bis the same cross-sectional view of the hollow composite constructiontube 308 shown in FIG. 14A, but shown with the secondary reinforcementmaterial, in this case concrete 310, within the tube 308.

In the embodiment illustrated in FIGS. 14A and 14B, an intermediate orshear transfer member or layer 312 is shown within the tube 308 eitherbonded to or cast into the inside surface 314 of the tube 308. Thesecondary structural reinforcement material 310 may then be insertedwithin the tube 308 to partially or completely fill the tube 308.

To form the tube 308 with the shear transfer layer 312, the sheartransfer layer 312 may be inserted into a mold assembly, such as themold assembly 202, between the bladder 204 and the fabric layer 206.After the fabric layer 206 is infused with the rigidification material232, and the rigidification material 232 hardens, the shear transferlayer 312 becomes bonded to the inside surface 314 of the tube 308, asshown in FIGS. 14A and 14B.

A first embodiment of the shear transfer layer 312 is shown in FIG. 15.The illustrated shear transfer layer 312 is a flexible, substantiallytubular member formed from a suitable material, such as but not limitedto polyethylene, polyester, and polyoxymethylene. The illustrated sheartransfer layer 312 includes a body formed as an array of elongatedmembers 316 and spaces 318 between the elongated members 316. In theillustrated embodiment, the shear transfer layer 312 defines a repeatingpattern of hexagons 313. When bonded to the inside surface 314 of thetube 308, and when viewed in transverse section such as shown in FIGS.14A and 14B, the elongated members define a pattern of alternatingprotrusions 316 and spaces between the protrusions 316, the spacesdefining regions 318 of no protrusions. The illustrated protrusions 316have substantially blunted or rounded radially inwardly facing edges320. The protrusions 316 extend outwardly and substantiallyperpendicularly from the inside surface 314, and thus substantiallyperpendicularly to the direction of the anticipated shear forces at theinterface 322 between the tube 308 and the secondary structuralreinforcement material 310. It will be understood that the sheartransfer layer 312 may comprise a repeating pattern or irregular arrayof any desired geometric shape or combination of shapes. Advantageously,the protrusions 316 and regions 318 of no protrusions defineperturbations of the otherwise relatively smooth inside surface 314 ofthe composite construction tube 308. The perturbations 316 and 318 havesufficient strength, stiffness, and proximity to substantially restrainin-plane relative motion between the primary and secondaryreinforcements 308 and 310 at their interface.

It will be also understood that the relative proportion of protrusions316 to regions 318 of no protrusions will be determined based on knownphysical properties of the materials interacting at the interface 322;i.e., the known physical properties of the tube 308 and the secondarystructural reinforcement material 310.

Referring now to FIG. 16, a portion of a second embodiment of the hybridcomposite construction member is shown at 332. The construction member332 is substantially similar to the construction member 302 and includesa hollow composite construction tube 334 having an inside surface 336.The inside surface 336 includes a pattern of alternating protrusions 338and regions 340 of no protrusions. The illustrated protrusions 338 havesubstantially blunted or rounded inwardly facing edges 342. Theprotrusions 338 need not be blunted to promote shear transfer, but bybeing blunted, the protrusions 338 offer protection against cracking ofthe secondary reinforcement material 310, particularly under fatigueloading. The protrusions 338 extend outwardly and substantiallyperpendicularly from the inside surface 336. In the illustratedembodiment, the protrusions 338 formed on the inside surface 336comprise a repeating pattern of diamonds. It will be understood that theprotrusions 338 may comprise a repeating pattern or irregular array ofany desired geometric shape or combination of shapes.

Referring now to FIG. 18, a portion of a first alternate embodiment ofthe mold assembly is shown at 402. To form the tube 334, an array, orrepeating pattern of diamonds or other geometric shapes may be formed asgrooves 346 in the outer surface 348 of an alternate embodiment of thebladder 344, as best shown in FIG. 18. It will be understood that thegrooves 346 may comprise a repeating pattern or irregular array of anydesired geometric shape or combination of shapes. After the fabric layer206 is infused with the rigidification material 232, and therigidification material 232 fills the grooves 346 and hardens, therepeating pattern of diamonds is formed into the inside surface 336 ofthe tube 334, as shown in FIG. 16.

Referring now to FIGS. 17 and 19, a portion of a third embodiment of thehybrid composite construction member is shown at 362. The constructionmember 362 includes a hollow composite construction tube 364 having aninside surface 366. The inside surface 366 includes a pattern ofalternating grooves 368 and regions 370 of no grooves. In theillustrated embodiment, the grooves 368 formed in the inside surface 366comprise a repeating pattern of diamonds. It will be understood that thegrooves 368 may comprise a repeating pattern or irregular array of anydesired geometric shape or combination of shapes.

Referring now to FIG. 19, a portion of a second alternate embodiment ofthe mold assembly is shown at 502. The mold assembly 502 is shown priorto the infusion of the rigidification material 232. To form the tube364, the repeating pattern 349 of diamonds or other geometric orirregular shapes may be formed as raised members or ribs 350 formed ontothe outer surface 352 of an alternate embodiment of the bladder 354, asbest shown in FIG. 19. After the fabric layer 206 is infused with therigidification material 232, the rigidification material 232 hardensaround the ribs 350, and the grooves 368 having a repeating diamondpattern are formed into the inside surface 366 of the tube 362, as shownin FIG. 17. It will be understood that the pattern 349 is shown as aregular repeating pattern, but the pattern 349 is not required to be aregular or repeating pattern to function as described herein. When therigidification material 232 hardens and the bladder 354 is removed, therepeating pattern of diamonds is formed into the inside surface 366 ofthe tube 364, as shown in FIG. 17.

Referring now to FIG. 20, a portion of a third alternate embodiment ofthe mold assembly is shown at 602 prior to the fabric layer 206 beinginfused with the rigidification material 232. The mold assembly 602 mayalso be used to form the tube 364. To form the tube 364, a mold patternmember 374 may be inserted into the mold assembly 602 between thebladder 204 and the fabric layer 206, as shown in FIG. 20. Theillustrated mold pattern member 374 is a flexible tubular member formedfrom a suitable material, such as polyethylene, polyester, andpolyoxymethylene.

The illustrated mold pattern member 374 includes a body formed as anarray of elongated members 378 and spaces 380 between the elongatedmembers 378. The mold pattern member 374 may define a repeating patternor irregular array of any desired geometric or non-geometric shape orcombination of shapes. When urged against the bladder 204, the elongatedmembers define a pattern of alternating protrusions 378 and spacesbetween the protrusions 378, the spaces defining regions 380 of noprotrusions.

As the fabric layer 206 is infused with the rigidification material 232,a vacuum (indicated by the arrow V in FIG. 22) may be applied to theinterstitial space 226 through the opening 220, as shown in FIG. 3.Atmospheric pressure within the interior cavity 201 (indicated by thearrow A in FIG. 22) acts on the interior wall 207 of the bladder 204.

The vacuum V and atmospheric pressure A urges the bladder 204 radiallyoutwardly against the mold pattern member 374. After the fabric layer206 is infused with the rigidification material 232, and therigidification material 232 hardens, the mold pattern member 374 may beremoved. As best shown in FIG. 21, the inside surface 372 of the fabriclayer 206 (now infused with rigidification material and defining thetube 364) includes the pattern of alternating grooves 368 formed by theprotrusion 378 and the regions 380 of no protrusions of the mold patternmember 374. As shown in FIG. 21, radially inwardly extending protrusions369 are defined between the grooves 368 on the inside surface 372 of thetube 364.

The mold pattern member 374 may be formed of a material to which the FRPresin or rigidification material 232 does not bond, thereby allowing themold pattern member 374 to be removed from the inside surface 372 afterthe resin 232 rigidifies.

Alternatively, the mold pattern member 374 may remain bonded to therigidification material 232 and the fabric layer 206, as shown in FIG.22. As shown in FIG. 22, the vacuum V and atmospheric pressure A urgesthe bladder 204 radially outwardly against the mold pattern member 374.The elongated members 378 define an array or pattern of ridges.Depressions 379 are formed on the inside surface 372 of the fabric layer206 when the bladder 204 is urged into the regions 380 of noprotrusions.

In the embodiments of the hybrid composite construction members 302,332, and 362 described above, a shear transfer promoting texture hasbeen applied to the inside surface 314, 334, and 364 of the hollowcomposite construction tube 308, 336, and 366, respectively. Such ashear transfer promoting texture allows more highly developed compositeaction between the primary reinforcement (i.e., the hollow compositeconstruction tubes 308, 336, and 366, respectively) and the secondaryreinforcement (i.e., the reinforcement material 310), relative to knowncomposite construction tubes. The more highly developed composite actionbetween the primary reinforcement and the secondary reinforcement causeshigher structural efficiency, and can promote longer fatigue life bypreventing wear or fretting at the interface between the primaryreinforcement and the secondary reinforcement. By adding the sheartransfer promoting texture to an already functional hybrid combinationof composite materials, a hybrid composite may be created. In thishybrid composite, maximum bending capacity before initial damage occursmay be increased, the ultimate load capacity may be increased, and insome applications, the long term durability of the hybrid compositeconstruction member 302 may be improved.

Advantageously, the addition of texture to the inside surface 314, 334,and 364 of the hollow composite construction tubes 308, 336, and 366,respectively, will provide increased strength. A further advantage ofthe embodiments of the composite construction members described hereinis that the illustrated composite construction members provide a regularpattern of alternating regions of protrusion and no protrusion withsubstantially blunted edges on the extremity of the protruding ridges.These blunted protrusions 338 offer protection against cracking of thesecondary reinforcement material 310, particularly under fatigueloading.

It will be understood that the percentage of the area of the insidesurface 314, 334, and 364 of the hollow composite construction tube 308,336, and 366, respectively, that is dedicated to protrusions, and themagnitude of the protrusions will depend on the materials interacting atthe interface.

The principle and mode of operation of the composite constructionmembers and methods of making such composite construction members havebeen described in its various embodiments. However, it should be notedthat the composite construction members and methods of making suchcomposite construction members described herein may be practicedotherwise than as specifically illustrated and described withoutdeparting from its scope.

1.-22. (canceled)
 23. An inflatable mold assembly for forming a hollowcomposite construction member suitable for use as a building material,the mold assembly having a longitudinal axis, and further having: aflexible, substantially tubular bladder wall defining an elongatedinflatable cavity; reinforcing fabric positioned concentrically aroundthe flexible bladder wall; a flexible air-impervious outer layerpositioned concentrically around the fabric, with the bladder wall andthe outer layer defining an elongated annular space, with the fabricbeing positioned within the space; and an intermediate shear transferlayer positioned concentrically within the elongated annular spacebetween the reinforcing fabric and the tubular bladder.
 24. Theinflatable mold assembly of claim 23 in which the mold is structured tobe bent into a curved shape after inflation to any one of many differentcurvatures, and in which the fabric is structured so that when tensionis applied to the fabric before bending the mold, the fibers of thefabric will remain in tension even after the mold is bent into thecurved shape.
 25. The inflatable mold assembly of claim 23 in which thefabric comprises a plurality of fibers, some of which are oriented in anoff-hoop direction that is at an angle greater than or equal to 30degrees to the hoop direction, and in which the fabric is structured sothat when tension is applied to the fabric, the off-hoop directionfibers are prevented from buckling when curvature is applied to the moldassembly resulting in superior structural properties relative to fabricto which tensioning was not applied.
 26. The inflatable mold assembly ofclaim 23 in which the elongated inflatable mold includes a mechanicalgrip at each end, with the mechanical grips being connected to thefabric and being configured to apply tension to the fabric.
 27. Theinflatable mold assembly of claim 23 in which the elongated inflatablecavity, when inflated, has a cross-sectional dimension that varies alongthe longitudinal axis of the elongated inflatable mold.
 28. Theinflatable mold assembly of claim 23 including a gripping system at eachend of the elongated inflatable mold.
 29. The inflatable mold assemblyof claim 28 including a vacuum inlet positioned outside of the grippingsystems.
 30. A hollow composite construction member suitable for use asa building material comprising: a curved tubular primary reinforcementmember having a hollow interior and formed from a first material; ashear transfer member bonded to an inside surface of the tubular primaryreinforcement member; and a secondary reinforcement material differentfrom the first material and at least partially filling the hollowinterior of the tubular primary reinforcement member.
 31. The hollowcomposite construction member of claim 30 wherein the secondaryreinforcement material is selected from the group consisting ofnon-shrink concrete, expansive concrete, non-shrink grout, expansivegrout, foam, and sand.
 32. The hollow composite construction memberaccording to claim 30, wherein the shear transfer member includes a bodyformed as an array of elongated members and spaces between the elongatedmembers.
 33. The hollow composite construction member according to claim32, wherein the array of elongated members and spaces define a repeatingpattern of geometric shapes.
 34. The hollow composite constructionmember according to claim 32, wherein the array of elongated members andspaces define an irregular array of dissimilar shapes.
 35. The hollowcomposite construction member according to claim 32, wherein theradially inwardly facing surfaces of the elongated members have arounded shape.
 36. The method according to claim 32, wherein the sheartransfer member is substantially tubular.
 37. The hollow compositeconstruction member according to claim 30, wherein the shear transfermember is formed from one of polyethylene, polyester, andpolyoxymethylene.
 38. A hollow composite construction member suitablefor use as a building material comprising: a curved tubular primaryreinforcement member having a hollow interior and formed from a firstmaterial, wherein one of an array of grooves and ridges is formed on aninside surface of the tubular primary reinforcement member, the arraydefining a shear transfer member; and a secondary reinforcement materialdifferent from the first material and at least partially filling thehollow interior of the tubular primary reinforcement member.
 39. Thehollow composite construction member of claim 38 wherein the secondaryreinforcement material is selected from the group consisting ofnon-shrink concrete, expansive concrete, non-shrink grout, expansivegrout, foam, and sand.
 40. The hollow composite construction memberaccording to claim 38, wherein the shear transfer member includes a bodyformed as an array of elongated members and spaces between the elongatedmembers.
 41. The hollow composite construction member according to claim40, wherein the array of elongated members and spaces define a repeatingpattern of geometric shapes.
 42. The hollow composite constructionmember according to claim 40, wherein the array of elongated members andspaces define an irregular array of dissimilar shapes.
 43. The hollowcomposite construction member according to claim 40, wherein theradially inwardly facing surfaces of the elongated members have arounded shape.
 44. The hollow composite construction member according toclaim 40, wherein the shear transfer member is substantially tubular.45. The hollow composite construction member according to claim 38,wherein the shear transfer member is formed from one of polyethylene,polyester, and polyoxymethylene.
 46. The inflatable mold assembly ofclaim 23 wherein the intermediate shear transfer layer positionedconcentrically within the elongated annular space between thereinforcing fabric and the tubular bladder comprises a layer having apattern of alternating protrusions with spaces between the protrusions.47. The inflatable mold assembly of claim 46 wherein the pattern ofalternating protrusions with spaces between the protrusions forms apattern of repeating hexagons.